Crystal Glass Article

Abstract

[Object] This invention relates to crystal glass article not containing lead or barium that can be chemical strengthened easily and that is highly alkali-resistant and equivalent to lead crystal glass in quality. [Solving Means] Crystal glass article that can be chemical strengthened easily and that is highly alkali-resistant and equivalent to lead crystal glass in quality can be produced with a glass composition containing: 62% to 65% by weight of SiO 2 ; 2% to 3.2% by weight of Al 2 O 3 ; 10% to 12% by weight of Na 2 O; 8% by weight to less than 10.0% by weight of K 2 O; 3% to 4.2% by weight of CaO; 2% to 3.2% by weight of SrO; 6% to 7.2% by weight of ZnO; 2.2% to 3% by weight of TiO 2 ; 0% to 0.4% by weight of Sb 2 O 3 ; and 0% to 1.2% by weight of SnO 2 +Y 2 O 3 +La 2 O 3 +ZrO 2 .

1 . Crystal glass article formed, of which glass having refractive index n d ≧1.53 and density ≧2.6 g/cm 3 , with a glass composition substantially not containing lead oxide PbO or barium oxide BaO, consisting essentially of in weight percent:
 62% to 65% by weight of SiO 2 ;   2% to 3.2% by weight of Al 2 O 3 ;   10% to 12% by weight of Na 2 O;   8% by weight to less than 10.0% by weight of K 2 O;   3% to 4.2% by weight of CaO;   2% to 3.2% by weight of SrO;   6% to 7.2% by weight of ZnO;   2.2% to 3% by weight of TiO 2 ;   0% to 0.4% by weight of Sb 2 O 3 ; and   0% to 1.2% by weight of SnO 2 +Y 2 O 3 +La 2 O 3 +ZrO 2 .   
   
   
       2 . The crystal glass article according to  claim 1 , wherein the glass is given chemically strengthened compressive stress layer having stress of larger than 1000 kg/cm 2  and thickness of greater than 20 μm by heat treatment for replacing sodium ions at the glass surface with potassium ions.